CN111052863A - Microwave heating device - Google Patents

Abstract

A microwave heating device (50) comprises: a heating chamber (2) for accommodating an object (1) to be heated; a magnetron (3) that generates microwaves; a waveguide (10) that transmits microwaves to the heating chamber (2); and a directional coupler (6) including a reflected wave detection unit that detects a part of the reflected wave. The directional coupler (6) is disposed at the position of an antinode (302) of an in-pipe standing wave (301) generated in the waveguide (10). According to this configuration, the detection accuracy of the reflected wave can be improved, and the state of the object (1) to be heated can be detected more accurately.

Description

Microwave heating device

Technical Field

The present disclosure relates to a microwave heating device such as a microwave oven.

Background

Conventionally, as such a microwave heating device, for example, a device disclosed in patent document 1 is known. The conventional microwave heating apparatus includes: a heating chamber for accommodating an object to be heated; a microwave generating unit for generating microwaves; and a waveguide that propagates the microwave to the heating chamber. A standing wave stabilizer is provided in the waveguide tube for stabilizing the position of an intra-tube standing wave generated in the waveguide tube. According to the conventional microwave heating apparatus, the microwave of a desired phase can be continuously radiated into the heating chamber by suppressing the positional deviation of the standing wave in the pipe by the standing wave stabilizing unit. As a result, the object to be heated in the heating chamber can be uniformly heated.

Patent documents 2 and 3 disclose microwave heating devices including: in order to prevent the microwave generating part from being damaged by the reflected wave returned from the heating chamber to the microwave generating part, a directional coupler for detecting the reflected wave is provided to the waveguide.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5816820

Patent document 2: japanese patent No. 6176540

Patent document 3: japanese patent No. 3331279

Disclosure of Invention

However, in the conventional microwave heating apparatus, there is still room for improvement from the viewpoint of more accurately detecting the state of the object to be heated which changes as the heating progresses. In particular, there is no study example focusing on the relationship between the detection accuracy of the reflected wave and the in-pipe standing wave in the waveguide, and it is not known at which position of the waveguide the directional coupler is disposed.

The purpose of the present disclosure is to provide a microwave heating device capable of improving the detection accuracy of reflected waves and more accurately detecting the state of an object to be heated.

A microwave heating device according to one embodiment of the present disclosure includes: a heating chamber for accommodating an object to be heated; a microwave generating unit for generating microwaves; a waveguide; and a reflected wave detection unit. The waveguide transmits the microwave generated by the microwave generating section to the heating chamber. The reflected wave detection unit is disposed in the vicinity of an antinode of a standing wave generated in the waveguide, and detects a part of the reflected wave, which is the microwave returned from the heating chamber to the microwave generation unit.

According to this aspect, the detection accuracy of the reflected wave can be improved, and the state of the object to be heated can be detected more accurately.

Drawings

Fig. 1 is a schematic view of a microwave heating apparatus of an embodiment of the present disclosure.

Fig. 2 is a schematic diagram showing a1 st modification of the microwave heating device according to the embodiment.

Fig. 3 is a schematic diagram showing a 2 nd modification of the microwave heating device according to the embodiment.

Fig. 4 is a schematic diagram showing a 3 rd modification of the microwave heating apparatus according to the embodiment.

Fig. 5 is a perspective view of the directional coupler of the embodiment.

Fig. 6 is a perspective view of the directional coupler according to the embodiment in a state where the printed circuit board is removed.

Fig. 7 is a plan view of the waveguide of the embodiment.

Fig. 8 is a circuit configuration diagram of a printed circuit board provided in the directional coupler according to the embodiment.

Fig. 9 is a diagram for explaining the principle of emitting circularly polarized microwaves from the cross apertures.

Fig. 10 is a diagram for explaining the direction and amount of microwaves that propagate through the microstrip line and change with time.

Fig. 11 is a diagram for explaining the direction and amount of microwaves that propagate through the microstrip line and change with time.

Fig. 12 is a plan view showing a1 st modification of the microstrip line.

Fig. 13 is a plan view showing a 2 nd modification of the microstrip line.

Fig. 14 is a plan view showing a 3 rd modification of the microstrip line.

Fig. 15 is a plan view showing a 4 th modification of the microstrip line.

Fig. 16 is a plan view showing a 5 th modification of the microstrip line.

Fig. 17 is a plan view showing a 6 th modification of the microstrip line.

Fig. 18 is a graph showing the relationship between the incident wave and the reflected wave that change with an increase in the temperature of the object, and the amount of absorption of the microwave by the object.

Fig. 19 is a plan view showing an orthogonal waveguide for evaluating detection accuracy of a reflected wave.

Fig. 20 is a characteristic diagram for measuring the detection accuracy of the reflected wave by the orthogonal waveguide for evaluation.

Fig. 21 is a schematic diagram showing a positional relationship between the reflected wave detection unit and the intra-tube standing wave in the waveguide.

Detailed Description

(discovery as a basis of the present disclosure)

The present inventors have conducted intensive studies to detect the state of an object to be heated more accurately, and as a result, have obtained the following findings.

The microwave generated by the microwave generating unit is propagated as an incident wave to the heating chamber through the waveguide. While a part of the microwaves propagating through the heating chamber is absorbed by the object to be heated, the other part of the microwaves returns from the heating chamber to the microwave generating unit through the waveguide as reflected waves.

Microwaves are hardly absorbed by ice, and on the other hand, are easily absorbed by water. Specifically, water absorbs about 8000 times more microwaves (based on dielectric loss coefficient) than ice. The microwaves are hardly absorbed by the water as the temperature of the water rises. Therefore, for example, in the case where the object to be heated is frozen food, the reflected wave and the amount of absorption of the microwave by the object to be heated have a relationship as shown in fig. 18.

Fig. 18 is a graph showing the relationship between the incident wave and the reflected wave that change with an increase in the temperature of the object, and the amount of absorption of the microwave by the object. In fig. 18, the horizontal axis represents the temperature of the object to be heated, and the vertical axis represents the signal intensity of the incident wave and the reflected wave. The graphs indicated by the broken line, the solid line, and the dashed line show the amount of absorption of microwaves by the incident wave, the reflected wave, and the object to be heated, respectively. The amount of microwave absorption by the object to be heated is the difference between the incident wave and the reflected wave.

As shown in fig. 18, in the initial stage of heating, the amount of microwave absorption by the object to be heated is small, and the reflected wave is large. The amount of microwave absorption by the object to be heated rapidly increases as the heating progresses and the ice melts, and the reflected wave rapidly decreases. When the ice is completely melted, the amount of microwave absorption by the object to be heated is maximized, and the reflected wave is minimized.

Then, the amount of microwave absorption by the object to be heated gradually decreases with the increase in water temperature, and the reflected wave gradually increases. Therefore, for example, by detecting a state where the reflected wave is minimized, the end of thawing of the frozen food can be detected.

The present inventors have found that the above-described relationship holds regardless of the weight, shape, and the like of an object to be heated, and that the state of the object to be heated can be detected more accurately from a change in the amount of reflected waves during heating.

A microwave heating device according to aspect 1 of the present disclosure includes: a heating chamber for accommodating an object to be heated; a microwave generating unit for generating microwaves; a waveguide; and a reflected wave detection unit. The waveguide transmits the microwave generated by the microwave generating section to the heating chamber. The reflected wave detection unit is disposed in the vicinity of an antinode of a standing wave generated in the waveguide, and detects a part of the reflected wave, which is the microwave returned from the heating chamber to the microwave generation unit.

In the microwave heating device according to claim 2 of the present disclosure, in addition to the first aspect 1, the reflected wave detection unit is disposed between two nodes of the standing wave in the pipe, and is thereby disposed in the vicinity of an antinode of the standing wave in the pipe.

In the microwave heating device according to claim 3 of the present disclosure, in addition to the aspect 2, the reflected wave detection unit is disposed in the vicinity of an antinode of the standing wave in the pipe by being disposed so as not to overlap with two nodes of the standing wave in the pipe.

In the microwave heating device according to claim 4 of the present disclosure, in addition to the aspect 3, the reflected wave detection unit is disposed in the vicinity of an antinode of the standing wave in the pipe by being spaced from the center position of the two nodes of the standing wave in the pipe by 1/8 or less of the wavelength in the pipe of the standing wave in the pipe.

In the microwave heating device according to aspect 5 of the present disclosure, in addition to aspect 1, the reflected wave detection unit is disposed in the vicinity of an antinode of the internal standing wave by being spaced apart from the end of the waveguide by a distance that is an odd multiple of 1/4 of the internal wavelength of the internal standing wave.

The microwave heating device according to claim 6 of the present disclosure further includes, in addition to the microwave heating device according to claim 1, a standing wave stabilizer that stabilizes a position of a standing wave generated in the waveguide. The reflected wave detection unit is disposed in the vicinity of an antinode of the standing wave in the pipe by being spaced apart from the standing wave stabilization unit by a distance that is an odd multiple of 1/4 times the in-pipe wavelength of the standing wave in the pipe.

In the microwave heating device according to claim 7 of the present disclosure, in addition to the microwave heating device according to claim 6, the standing wave stabilizer is constituted by a protrusion protruding into the waveguide.

In the microwave heating device according to claim 8 of the present disclosure, in addition to the first aspect 6, the waveguide has a bent portion that is bent in an L shape, and the standing wave stabilizing portion is constituted by the bent portion.

In the microwave heating device according to claim 9 of the present disclosure, in addition to the first aspect, the reflected wave detection unit is disposed in the vicinity of an antinode of the internal standing wave by being spaced apart from the coupling position of the microwave generation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the internal wavelength of the internal standing wave.

A microwave heating apparatus according to claim 10 of the present disclosure includes, in addition to the first aspect, a microwave radiation unit that radiates microwaves transmitted through a waveguide to a heating chamber. The reflected wave detection unit is disposed in the vicinity of an antinode of the in-tube standing wave by being spaced apart from the coupling position of the microwave radiation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the in-tube wavelength of the in-tube standing wave.

In the microwave heating device according to claim 11 of the present disclosure, in addition to the first aspect, the reflected wave detection unit includes: an opening portion provided in the waveguide; and a coupling line facing the opening. The opening is disposed in the vicinity of an antinode of the standing wave in the pipe.

In the microwave heating device according to claim 12 of the present disclosure, in addition to the 11 th aspect, the opening portion includes the 1 st long hole and the 2 nd long hole that intersect with each other, and is provided at a position that does not intersect with the tube axis of the waveguide in a plan view, and an opening intersection portion where the 1 st long hole and the 2 nd long hole intersect is disposed in the vicinity of an antinode of the in-tube standing wave.

Hereinafter, a microwave heating device according to an embodiment of the present disclosure will be described with reference to the drawings.

(embodiment mode)

Fig. 1 is a schematic view of a microwave heating apparatus 50 of an embodiment of the present disclosure. As shown in fig. 1, the microwave heating apparatus 50 includes a heating chamber 2 for accommodating an object 1 to be heated, a magnetron 3, and a waveguide 10. The magnetron 3 is an example of a microwave generating unit that generates microwaves. The waveguide 10 transmits the microwave generated by the magnetron 3 to the heating chamber 2.

The object 1 to be heated is, for example, a frozen food. The heating chamber 2 is formed of, for example, a rectangular parallelepiped case. The heating chamber 2 is provided with a mounting table 2a on which the object 1 is placed. The mounting table 2a is made of a material that is easily transparent to microwaves, such as glass or ceramic.

The waveguide 10 is a square waveguide having a cross section formed in a rectangular shape. The antenna 4 is disposed below the mounting table 2 a. The microwave propagating through the waveguide 10 is radiated into the heating chamber 2 through the antenna 4 as an example of a microwave radiation unit.

By this microwave, an in-tube standing wave of the microwave is generated in the waveguide 10 in the transmission direction of the microwave from the magnetron 3 toward the antenna 4. Fig. 1 schematically shows an in-pipe standing wave generated inside a waveguide 10. The in-tube wavelength λ g of the waveguide 10 is determined according to the oscillation frequency of the magnetron 3 and the shape of the waveguide 10.

The intra-tube standing wave has an antinode and a node which repeat in the longitudinal direction of the waveguide 10 by 1/2 lengths of each intra-tube wavelength λ g. The end of the waveguide 10 in the transmission direction of the microwave necessarily generates a node. An antinode is inevitably generated in a portion of the magnetron 3 from which the microwave is radiated.

A standing wave stabilizer 5 is provided in the waveguide 10, and the standing wave stabilizer 5 stabilizes the position of an intra-tube standing wave generated in the waveguide 10. In the present embodiment, the standing wave stabilizer 5 is a protrusion configured to partially narrow the waveguide 10 by protruding into the waveguide 10.

The standing wave stabilizer 5 matches the impedance near the magnetron 3 in the waveguide 10 with the impedance near the heating chamber 2. The standing wave stabilizer 5 is disposed at a distance of an integral multiple of 1/2 of the in-tube wavelength λ g from the end of the waveguide 10 in the propagation direction of the microwave. Thereby, the standing wave stabilizer 5 fixes the node of the in-pipe standing wave in the vicinity of the standing wave stabilizer 5.

A directional coupler 6 is provided on a wall surface (Wide Plane) of the waveguide 10, and the directional coupler 6 functions as both an incident wave detection unit and a reflected wave detection unit. The incident wave detection unit detects a microwave propagating from the magnetron 3 to the heating chamber 2, that is, a part of the incident wave. The reflected wave detector detects a part of the reflected wave, which is the microwave returned from the heating chamber 2 to the magnetron 3.

The directional coupler 6 is disposed closer to the heating chamber 2 than the standing wave stabilizer 5. Specifically, the directional coupler 6 and the standing wave stabilizer 5 are arranged at a distance that is an odd multiple (1 time in the present embodiment) of 1/4 of the in-tube wavelength λ g of the in-tube standing wave in the propagation direction of the microwave (the left-right direction in fig. 1). The directional coupler 6 is disposed between the standing wave stabilizer 5 and the antenna 4.

Directional coupler 6 detects detection signal 6a and detection signal 6b from the incident wave and the reflected wave, respectively, and transmits detection signal 6a and detection signal 6b to control unit 7. The specific structure of the directional coupler 6 is described in detail later.

The control unit 7 receives a signal 7a in addition to the detection signals 6a, 6 b. The signal 7a includes the heating condition set by an input unit (not shown) of the microwave heating device 50, and the weight of the object 1 to be heated and the amount of steam detected by a sensor (not shown).

The control section 7 controls the driving power source 8 and the motor 9 based on the detection signals 6a, 6b and the signal 7 a. The driving power supply 8 supplies power for generating microwaves to the magnetron 3. The motor 9 rotates the antenna 4. In this way, the microwave heating device 50 heats the object 1 to be heated stored in the heating chamber 2 by the microwaves supplied to the heating chamber 2.

In the present embodiment, the directional coupler 6 is closer to the heating chamber 2 than the standing wave stabilizer 5. With this configuration, the influence of the directional coupler 6 from the standing wave stabilizer 5 can be reduced. This enables the state of the object 1 to be detected more accurately. As a result, for example, the thawing state of the frozen food can be accurately grasped. By controlling the amount of heating in accordance with this, the thawing time can be shortened.

In the present embodiment, the directional coupler 6 and the standing wave stabilizer 5 are arranged at a distance in the transmission direction of the microwave that is an odd multiple of 1/4 of the in-tube wavelength λ g of the in-tube standing wave. With this configuration, the directional coupler 6 can be disposed in the vicinity of the antinode of the standing wave in the pipe. Therefore, the amount of the reflected wave received by the directional coupler 6 can be increased, thereby improving the detection accuracy of the reflected wave. As a result, the state of the object 1 can be detected more accurately.

The positions of the directional coupler 6 and the standing wave stabilizer 5 in the width direction (depth direction in fig. 1) of the waveguide 10 are not particularly limited. The directional coupler 6 and the standing wave stabilizer 5 may be arranged at a distance substantially equal to an odd multiple of 1/4 of the in-tube wavelength λ g.

When the temperature of the object 1 to be heated is high at the start of heating or when the weight of the object 1 is heavy, the amount of reflected waves does not change much. Therefore, it is sometimes difficult to determine the state where the reflected wave is minimal.

In the present embodiment, the directional coupler 6 has functions of both an incident wave detection unit and a reflected wave detection unit. With this configuration, the amount of microwaves absorbed by the object 1 can be estimated more accurately from the incident wave and the reflected wave detected by the directional coupler 6. For example, by detecting a change in reflectance obtained by dividing the amount of reflected waves by the amount of incident waves, it is easy to determine that the reflected waves are in the minimum state. As a result, the state of the object 1 can be detected more accurately.

In the present embodiment, the directional coupler 6 has functions of both an incident wave detection unit and a reflected wave detection unit. However, the present disclosure is not limited thereto. The incident wave detector and the reflected wave detector may be provided separately. The incident wave detection unit may be located closer to the magnetron 3 than the standing wave stabilization unit 5.

In the present embodiment, one directional coupler 6 is disposed closer to the heating chamber 2 than the standing wave stabilizer 5. However, the present disclosure is not limited thereto. Fig. 2 is a schematic diagram showing a1 st modification of the microwave heating device 50. Fig. 2 also schematically shows an in-tube standing wave generated inside the waveguide 10, as in fig. 1.

As shown in fig. 2, microwave heating apparatus 50 according to modification 1 includes directional coupler 60 in addition to directional coupler 6, and directional coupler 60 has the same configuration as directional coupler 6. That is, the directional coupler 60 has a 2 nd reflected wave detection section, and the 2 nd reflected wave detection section has the same configuration as the reflected wave detection section provided in the directional coupler 6. The directional coupler 60 is disposed closer to the magnetron 3 than the standing wave stabilizer 5.

According to this configuration, the 2 nd reflected wave detection unit can also detect a part of the reflected wave that returns to the magnetron 3 through the standing wave stabilizer 5. Thus, for example, when the amount of the reflected wave is very large, the magnetron 3 can be stopped, and a failure of the magnetron 3 can be prevented.

In the present embodiment, the standing wave stabilizer 5 is constituted by a protrusion protruding into the waveguide 10. However, the standing wave stabilizer 5 is not limited to the present embodiment as long as it can stabilize the position of the standing wave in the tube by locally narrowing the waveguide 10 to disturb the propagation of the microwave.

Fig. 3 is a schematic diagram showing a 2 nd modification of the microwave heating device 50. Fig. 3 also schematically shows an in-tube standing wave generated inside the waveguide 10, as in fig. 1 and 2. As shown in fig. 3, the waveguide 10 has a bent portion 10b bent in an L shape.

In this case, the cross-sectional area of the bent portion 10b shown by the broken line in fig. 3 is larger than the cross-sectional area of the other portion of the waveguide 10. Therefore, the node of the in-pipe standing wave is easily fixed to the center of the bent portion 10b (the center of the broken line in fig. 3). In modification 2, the bent portion 10b constitutes the standing wave stabilizer 5.

The waveguide 10 shown in fig. 1 is a square waveguide having a uniform cross-sectional area except for the portion where the standing wave stabilizer 5 is arranged. However, the present disclosure is not limited thereto. Fig. 4 is a schematic diagram showing a 3 rd modification of the microwave heating device 50. Fig. 4 also schematically shows an in-tube standing wave generated inside the waveguide 10, as in fig. 1 to 3.

As shown in fig. 4, in modification 3, the waveguide 10 is a square waveguide whose sectional area gradually decreases from the magnetron 3 toward the heating chamber 2. The waveguide 10 of modification 3 does not have a locally narrow portion except for the standing wave stabilizer 5. Therefore, the waveguide 10 according to modification 3 can obtain the same effect as the waveguide 10 shown in fig. 1.

The standing wave stabilizer 5 shown in fig. 1 is constituted by one element. However, the standing wave stabilizer 5 may be configured by a plurality of elements. In this case, the directional coupler 6 may be disposed closer to the heating chamber 2 than the structural member of the standing wave stabilizer 5 disposed closest to the heating chamber 2.

In the present embodiment, the motor 9 rotates the antenna 4. However, the present disclosure is not limited thereto. For example, the antenna 4 may be an opening formed to radiate the microwave propagating through the waveguide 10 into the heating chamber 2 as a circularly polarized microwave.

Next, the structure of the directional coupler 6 will be explained. Fig. 5 is a perspective view of the directional coupler 6. Fig. 6 is a perspective view of the directional coupler 6 in a state where the printed board 12 is removed. Fig. 7 is a top view of the waveguide 10. Fig. 8 is a circuit configuration diagram of the printed board 12 provided in the directional coupler 6.

Fig. 1 to 4 show that the directional coupler 6 is provided on the bottom wall of the waveguide 10. However, fig. 5 and 6 show that the directional coupler 6 is provided on the upper wall of the waveguide 10 for easy understanding. In the present embodiment, the cross section perpendicular to the tube axis L1 of the waveguide 10 has a rectangular shape. The tube axis L1 is the central axis in the width direction of the waveguide 10.

The directional coupler 6 has a cross opening 11, a printed substrate 12, and a support portion 14. The intersection opening 11 is an X-shaped opening disposed on the wide width surface 10a of the waveguide 10. The printed substrate 12 is disposed outside the waveguide 10 so as to face the intersection opening 11. The support portion 14 supports the printed substrate 12 on the outer surface of the waveguide 10.

As shown in fig. 7, the intersection opening 11 is disposed at a position not intersecting the tube axis L1 of the waveguide 10 in a plan view. The opening center portion 11c of the intersection opening 11 is disposed at a distance D1 from the tube axis L1 of the waveguide 10 in plan view. Dimension D1 is, for example, 1/4 of the width of waveguide 10. The cross opening 11 emits the microwave propagating through the waveguide 10 toward the printed substrate 12 as a circularly polarized microwave.

The opening shape of the intersection opening 11 is determined according to the conditions such as the width and height of the waveguide 10, the power level and frequency band of the microwave propagating through the waveguide 10, and the power level of the circularly polarized microwave radiated from the intersection opening 11.

For example, in the case where the width of the waveguide 10 is 100mm, the height is 30mm, the wall thickness of the waveguide 10 is 0.6mm, the maximum power level of the microwave propagating in the waveguide 10 is 1000W, the frequency band is 2450MHz, and the maximum power level of the circularly polarized microwave radiated from the intersection 11 is about 10mW, the length 11W and the width 11d of the intersection 11 are determined to be 20mm, 2mm, respectively.

As shown in fig. 8, the cross opening 11 includes a1 st long hole 11e and a 2 nd long hole 11f that cross each other. The opening center portion 11c of the intersecting opening 11 coincides with an opening intersecting portion where the 1 st long hole 11e and the 2 nd long hole 11f intersect. The intersection opening 11 is formed line-symmetrically with respect to the perpendicular line L2. Perpendicular line L2 is perpendicular to tube axis L1 and passes through opening center portion 11 c.

In the present embodiment, the 1 st long hole 11e and the 2 nd long hole 11f intersect at an angle of 90 degrees. However, the present disclosure is not limited thereto. The 1 st long hole 11e and the 2 nd long hole 11f may intersect at an angle of 60 degrees or 120 degrees.

When the opening center portion 11c of the cross opening 11 is disposed at a position overlapping the pipe axis L1 in a plan view, the electric field reciprocates along the transmission direction of the microwave without rotating. In this case, the cross opening 11 radiates polarized microwaves.

If the opening center portion 11c is slightly deviated from the tube axis L1, the electric field rotates. However, when the opening center portion 11c approaches the tube axis L1 (the closer to 0mm the dimension D1), an irregular rotating electric field is generated. In this case, the cross hatch 11 radiates elliptically polarized microwaves.

In the present embodiment, the dimension D1 is set to be about 1/4 of the width of the waveguide 10. In this case, a substantially standard circular rotating electric field is generated. The cross hatch 11 emits a substantially standard circular circularly polarized microwave. Therefore, the rotation direction of the circularly polarized microwave becomes more definite. As a result, the incident wave and the reflected wave can be separated and detected with high accuracy.

The printed circuit board 12 includes: a substrate back surface 12b facing the intersection opening 11; and a substrate front side 12a opposite the substrate back side 12 b. The substrate front surface 12a has a copper foil (not shown) formed to cover the entire substrate front surface 12a, as an example of the microwave reflecting member. The copper foil prevents the circularly polarized microwaves emitted from the intersection opening 11 from transmitting through the printed circuit board 12.

As shown in fig. 8, a microstrip line 13 as an example of a coupling line is disposed on the substrate back surface 12 b. The microstrip line 13 is constituted by a transmission line having a characteristic impedance of approximately 50 Ω, for example. The microstrip line 13 is disposed so as to surround the opening center portion 11c of the cross opening 11.

Hereinafter, the effective length λ of the microstrip line 13_reThe description is given. When the width of the microstrip line 13 is w, the thickness of the printed board 12 is h, the speed of light is c, the frequency of the electromagnetic wave is f, and the relative dielectric constant of the printed board is epsilon_rThe effective length λ of the microstrip line 13_reRepresented by the following formula. Effective length λ_reIs the wavelength of the electromagnetic wave propagating in the microstrip line 13.

[ formula 1]

Specifically, the microstrip line 13 has a1 st transmission line 13a and a 2 nd transmission line 13 b. The 1 st transmission line 13a includes a1 st straight line portion 13aa as an example of a1 st crossover portion. The 1 st linear portion 13aa intersects the 1 st elongated hole 11e at a position farther from the tube axis L1 than the opening center portion 11c in plan view. The 1 st linear portion 13aa extends away from the tube axis L1 as it approaches the perpendicular line L2.

The 2 nd transmission line 13b has a 2 nd straight line portion 13ba as an example of the 2 nd intersecting line portion. The 2 nd linear portion 13ba intersects the 2 nd elongated hole 11f at a position farther from the tube axis L1 than the opening center portion 11c in plan view. The 2 nd linear portion 13ba extends away from the tube axis L1 as approaching the perpendicular line L2. First linear portion 13aa and second linear portion 13ba are arranged line-symmetrically with respect to perpendicular line L2.

The 1 st transmission line 13a and the 2 nd transmission line 13b are connected to each other at the following positions: this position is outside the rectangular region E1 in plan view and is farther from the tube axis L1 than the rectangular region E1. The 1 st linear portion 13aa intersects the 1 st long hole 11e at a position closer to the opening distal end portion 11ea than the opening central portion 11c in a plan view.

The 1 st linear portion 13aa is perpendicular to the 1 st elongated hole 11e in a plan view. The 2 nd straight portion 13ba intersects the 2 nd long hole 11f at a position closer to the opening distal end portion 11fa than the opening center portion 11c in a plan view. The 2 nd linear portion 13ba is perpendicular to the 2 nd elongated hole 11f in a plan view.

One end of the 1 st transmission line 13a and one end of the 2 nd transmission line 13b are connected to each other outside the region overlapping the intersection opening 11 in a plan view. One end of the 1 st linear portion 13aa is connected to one end of the 2 nd linear portion 13ba outside the rectangular region E1 circumscribed with the cross opening 11.

The 1 st coupling point P1 is in top viewThe 1 st linear portion 13aa and the 1 st elongated hole 11e intersect with each other when viewed. The 2 nd coupling point P2 is a point at which the 2 nd linear portion 13ba and the 2 nd elongated hole 11f intersect with each other in a plan view. Let the straight line connecting the 1 st coupling point P1 and the 2 nd coupling point P2 be an imaginary straight line L3. In the present embodiment, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b farther from the tube axis L1 than the virtual straight line L3 is set to the effective length λ _re1/4 of (1).

A line passing through the opening center portion 11c in plan view and parallel to the tube axis L1 is a parallel line L4. In the present embodiment, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b that are farther from the tube axis L1 than the parallel line L4 is set to the effective length λ _re1/2 of (1).

The 1 st transmission line 13a has a 3 rd linear portion 13ab, and the 3 rd linear portion 13ab connects the other end of the 1 st linear portion 13aa to the 1 st output portion 131. The 1 st linear portion 13aa and the 3 rd linear portion 13ab are connected to form an obtuse angle (e.g., 135 degrees).

The 2 nd transmission line 13b has a 4 th straight portion 13bb, and the 4 th straight portion 13bb connects the other end of the 2 nd straight portion 13ba with the 2 nd output portion 132. The 2 nd and 4 th linear portions 13ba and 13bb are connected to form an obtuse angle (e.g., 135 degrees). The 3 rd and 4 th linear portions 13ab and 13bb are arranged parallel to the perpendicular line L2.

The 1 st output unit 131 and the 2 nd output unit 132 are disposed outside the support portion 14 (see fig. 5 and 6) in a plan view. The 1 st output unit 131 is connected to the 1 st detector circuit 15. The 1 st detector circuit 15 detects the level of the microwave signal and outputs the detected level of the microwave signal as a control signal. The 2 nd output unit 132 is connected to the 2 nd detector circuit 16. The 2 nd detector circuit 16 detects the level of the microwave signal and outputs the detected level of the microwave signal as a control signal.

In the present embodiment, each of the 1 st detector circuit 15 and the 2 nd detector circuit 16 includes a smoothing circuit (not shown) including a chip resistor and a schottky diode. The 1 st detector circuit 15 rectifies the microwave signal from the 1 st output unit 131, and converts the rectified microwave signal into a dc voltage. The converted dc voltage is output to the 1 st detection output unit 18. The 1 st detection output unit 18 transmits the detection signal 6a corresponding to the incident wave to the control unit 7 (see fig. 1).

Similarly, the 2 nd detector circuit 16 rectifies the microwave signal from the 2 nd output unit 132, and converts the rectified microwave signal into a dc voltage. The converted dc voltage is output to the 2 nd detection output unit 19. The 2 nd detection output unit 19 transmits the detection signal 6b corresponding to the reflected wave to the control unit 7 (see fig. 1).

Printed circuit board 12 has four holes ( holes 20a, 20b, 20c, and 20d) for mounting printed circuit board 12 to waveguide 10. Copper foil is formed as a ground around the holes 20a, 20b, 20c, 20d on the substrate back surface 12 b. The portion where the copper foil is formed has the same potential as the substrate front surface 12 a.

The printed circuit board 12 is fixed to the waveguide 10 by being screwed to the support portion 14 by screws 201a, 201b, 201c, and 201d (see fig. 5) through holes 20a, 20b, 20c, and 20 d.

As shown in fig. 6, the support portion 14 has threaded portions 202a, 202b, 202c, and 202d for screwing screws 201a, 201b, 201c, and 201d, respectively, to the threaded portions 202a, 202b, 202c, and 202 d. The threaded portions 202a, 202b, 202c, 202d are formed in the flange portion provided to the support portion 14.

The support portion 14 has conductivity and is disposed so as to surround the intersection opening 11 in a plan view. The support portion 14 functions as a shield for preventing the circularly polarized microwaves emitted from the cross hatch 11 from leaking to the outside of the support portion 14.

The support portion 14 has a groove 141 and a groove 142 through which the 3 rd and 4 th linear portions 13ab and 13bb of the microstrip line 13 pass. According to this configuration, the 1 st output portion 131 and the 2 nd output portion 132 of the microstrip line 13 can be disposed outside the support portion 14. The grooves 141 and 142 function as extraction portions for extracting the microwave signal propagating through the microstrip line 13 to the outside of the support portion 14. The grooves 141 and 142 can be formed by recessing the flange portion of the support portion 14 so as to be away from the printed circuit board 12.

Fig. 5 and 6 show a connector 18a and a connector 19a connected to the 1 st detection output unit 18 and the 2 nd detection output unit 19 shown in fig. 8, respectively.

In the present embodiment, the directional coupler 6 has functions of both an incident wave detection unit and a reflected wave detection unit. However, the present disclosure is not limited thereto. The directional coupler 6 may be configured to function as only one of the incident wave detector and the reflected wave detector. In this case, the directional coupler 6 is configured by replacing one of the 1 st detector circuit 15 and the 2 nd detector circuit 16 shown in fig. 8 with a termination circuit (for example, a chip resistor of 50 Ω).

Next, the operation and action of the directional coupler 6 will be described.

First, the principle of emitting circularly polarized microwaves from the cross hatch 11 will be described with reference to fig. 9. In fig. 9, a magnetic field distribution 10d generated in the waveguide 10 is represented by a concentric ellipse of a broken line. The direction of the magnetic field distribution 10d is indicated by an arrow. The magnetic field distribution 10d moves in the waveguide 10 in the microwave propagation direction a1 with time.

At time t shown in fig. 9 (a), t0, the magnetic field distribution 10d is formed. At this time, the slot 1e of the cross opening 11 is excited by a magnetic field indicated by a broken-line arrow B1. At time t shown in fig. 9 (B), t0+ t1, the 2 nd long hole 11f of the cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B2.

At time T shown in fig. 9 (c), T0+ T/2(T is the period of the in-tube wavelength λ g of the microwave), the 1 st slot 11e of the cross slit 11 is excited by a magnetic field indicated by a broken-line arrow B3. At time T shown in fig. 9 (d), T0+ T/2+ T1, the 2 nd long hole 11f of the cross opening 11 is excited by a magnetic field indicated by a broken-line arrow B4. At time T, T0+ T, the 1 st long hole 11e of the cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B1, as in the case of time T, T0.

By repeating these states in sequence, the circularly polarized microwaves rotating counterclockwise (the microwave rotation direction 32) are radiated from the intersection opening 11 to the outside of the waveguide 10.

Here, when the microwave propagating along arrow 30 shown in fig. 7 is an incident wave and the microwave propagating along arrow 31 is a reflected wave, the incident wave propagates in the same direction as propagation direction a1 shown in fig. 9. Therefore, as described above, the circularly polarized microwaves rotating counterclockwise are radiated from the intersection opening 11 to the outside of the waveguide 10. On the other hand, the reflected wave propagates in the direction opposite to the propagation direction a1 shown in fig. 9. Therefore, the microwave of circular polarization rotating in the clockwise direction is radiated from the intersection opening 11 to the outside of the waveguide 10.

The circularly polarized microwaves radiated to the outside of the waveguide 10 are coupled to the microstrip line 13, the microstrip line 13 being opposed to the intersection opening 11. The microstrip line 13 outputs most of the microwaves radiated from the intersection 11 by the incident wave propagating along the arrow 30 to the 1 st output unit 131.

On the other hand, the microstrip line 13 outputs most of the microwaves radiated from the cross opening 11 by the reflected waves propagating along the arrow 31 to the 2 nd output unit 132. This makes it possible to separate and detect the incident wave and the reflected wave with higher accuracy. This point is explained in more detail with reference to fig. 10.

Fig. 10 is a diagram for explaining the direction and amount of the microwave that propagates through the microstrip line 13 and changes with time. A gap exists between the microstrip line 13 and the cross opening 11. The time originally required for the microwaves to reach the microstrip line 13 delays the time for the microwaves to propagate in the gap. However, for convenience, it is assumed here that this time delay does not exist.

Here, a region where the intersection opening 11 intersects with the microstrip line 13 in a plan view is referred to as a coupling region. The 1 st coupling point P1 is substantially the center of the coupling region where the 1 st long hole 11e intersects the microstrip line 13. The 2 nd coupling point P2 is substantially the center of the coupling region where the 2 nd long hole 11f intersects the microstrip line 13.

In fig. 10, the amount of microwaves (current flowing through the magnetic field linkage) propagating through the microstrip line 13 is represented by the thickness of the solid arrow line. That is, when the amount of microwaves propagating through the microstrip line 13 is large, the line is thick, and when the amount of microwaves propagating through the microstrip line 13 is small, the line is thin.

At time t shown in fig. 10 (a), t0, the 1 st slot 11e of the cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B1, and a microwave indicated by a thick solid-line arrow M1 is generated at the 1 st coupling point P1. The microwave propagates in the microstrip line 13 toward the 2 nd coupling point P2.

At time t shown in fig. 10 (B), t0+ t1, the 2 nd long hole 11f of the cross opening 11 is excited by a magnetic field indicated by a broken-line arrow B2, and a microwave indicated by a thick solid-line arrow M2 is generated at the 2 nd coupling point P2.

When the effective propagation time of the microwave based on the microstrip line 13 between the 1 st coupling point P1 and the 2 nd coupling point P2 is designed as time t1, the microwave generated at the 1 st coupling point P1 at the time shown in (a) of fig. 10 propagates to the 2 nd coupling point P2 at the time shown in (b) of fig. 10. That is, at the time shown in fig. 10 (b), microwaves indicated by solid arrows M1 and microwaves indicated by solid arrows M2 are generated at the 2 nd coupling point P2.

Therefore, the two microwaves are added and propagated through the microstrip line 13 toward the 2 nd output unit 132, and after a predetermined time has elapsed, the two microwaves are output to the 2 nd output unit 132. In the present embodiment, in order to set the effective propagation time to the time t1, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b farther from the tube axis L1 than the virtual straight line L3 is set to the effective length λ _re1/4 of (1). With this configuration, the microstrip line 13 can be easily designed.

At time T shown in fig. 10 (c), T0+ T/2 excites the 1 st slot 11e of the cross opening 11 with a magnetic field indicated by a broken-line arrow B3, and a microwave indicated by a thin solid-line arrow M3 is generated at the 1 st coupling point P1. The microwave propagates through the microstrip line 13 toward the 1 st output unit 131, and is output to the 1 st output unit 131 after a predetermined time has elapsed.

The reason why the thickness of the solid arrow M3 is smaller than the thickness of the solid arrow M1 is as follows. As described above, the circularly polarized microwaves rotating counterclockwise (the rotation direction 32 of the microwaves) are radiated from the cross hatch 11.

At the time shown in fig. 10 (a), the microwave indicated by the solid arrow M1 generated at the 1 st coupling point P1 propagates in substantially the same direction as the rotational direction of the microwave radiated from the intersection 11. Therefore, the energy of the microwave represented by the solid arrow M1 is not reduced.

On the other hand, at the time shown in fig. 10 (c), the microwave indicated by the solid arrow M3 generated at the 1 st coupling point P1 propagates in a direction substantially opposite to the rotational direction of the microwave radiated from the cross hatch 11. Thus, the energy of the coupled microwaves is reduced. Therefore, the amount of microwaves indicated by the solid arrow M3 is smaller than the amount of microwaves indicated by the solid arrow M1.

At time T shown in fig. 10 (d), T0+ T/2+ T1, the 2 nd long hole 11f of the cross opening 11 is excited by a magnetic field indicated by a broken-line arrow B4, and a microwave indicated by a thin solid-line arrow M4 is generated at the 2 nd coupling point P2. The microwave propagates toward the 1 st coupling point P1. The reason why the solid arrow M4 is reduced in thickness is the same as the reason why the solid arrow M3 is reduced in thickness.

At time T, T0+ T, the 1 st long hole 11e of the cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B1, similarly to time T, T0 shown in fig. 10 (a). In this case, the microwave represented by a thin solid arrow M4, which is not described in the case of the time shown in fig. 10 (a), exists on the microstrip line 13.

The microwave, which is indicated by a thin solid arrow M4, propagates to the 1 st coupling point P1 at time T (T0 + T) (i.e., T0). The microwave represented by the thin solid arrow M4 propagates in the opposite direction to the microwave represented by the thick solid arrow M1. Therefore, the microwaves indicated by the solid arrow M4 are cancelled and reduced, and are not output to the 1 st output unit 131.

Strictly speaking, the amount of microwaves propagating from the 1 st coupling point P1 at time t0 is obtained by subtracting the amount of microwaves indicated by the thin solid arrow M4 from the amount of microwaves indicated by the thick solid arrow M1 (M1-M4). Therefore, the amount of microwaves output to the 2 nd output unit 132 is obtained by adding the amount of microwaves propagating from the 2 nd coupling point P2 to the amount of microwaves indicated by the thick solid arrow M2 (M1+ M2-M4).

Even if this is considered, the amount of microwaves (M1+ M2-M4) output to the 2 nd output part 132 is much more than the amount of microwaves (M3) output to the 1 st output part 131. Therefore, the microstrip line 13 outputs most of the microwaves radiated counterclockwise from the cross opening 11 by the reflected waves propagating along the arrow 31 to the 2 nd output unit 132. On the other hand, the microstrip line 13 outputs most of the microwaves radiated in the clockwise direction from the intersection 11 by the incident wave propagating along the arrow 30 to the 1 st output unit 131.

The amount of microwaves radiated from the intersection opening 11 with respect to the amount of microwaves propagating in the waveguide 10 is determined according to the shapes and sizes of the waveguide 10 and the intersection opening 11. For example, with the above-described shape and size, the amount of microwaves radiated from the intersection opening 11 with respect to the amount of microwaves propagating in the waveguide 10 is about 1/100000 (about-50 dB).

Next, in the present embodiment, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b, which are farther from the pipe axis L1 than the parallel line L4, is set to the effective length λ_reThe reason of 1/2 (1) is explained.

Fig. 11 is a diagram for explaining the direction and amount of the microwave that propagates through the microstrip line 13 and changes with time. Fig. 11 (a) to (d) are diagrams showing states after the elapse of time t1/2 from fig. 10 (a) to (d), respectively.

Although not described in the above description, the magnetic field distribution 10d moves in the propagation direction a1 of the microwave in the waveguide 10 with time. Therefore, as shown in (a) to (d) of fig. 11, the slot 1, the slot 11e, and the slot 2, the slot 11f are excited by the magnetic fields indicated by the broken arrows B12, B23, B34, and B41. Thereby, the circularly polarized microwaves radiated to the outside of the waveguide 10 are coupled to the microstrip line 13.

Here, a region where perpendicular line L2 and parallel line L4 intersect microstrip line 13 in a plan view is referred to as a coupling region. The 3 rd coupling point P3 is substantially the center of the coupling region where the perpendicular line L2 intersects the microstrip line 13. The 4 th coupling point P4 is substantially the center of the coupling region where the parallel line L4 crosses the 1 st transmission line 13 a. The 5 th coupling point P5 is substantially the center of the coupling region where the parallel line L4 crosses the 2 nd transmission line 13 b.

At time t shown in fig. 11 (a), t0+ t1/2, cross hatch 11 is excited by a magnetic field indicated by broken line arrow B12, and a microwave indicated by thick solid line arrow M11 is generated at coupling point 3P 3. The microwave propagates in the microstrip line 13 toward the 5 th coupling point P5.

At time t shown in fig. 11 (B), t0+ t1+ t1/2, the cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B23. Microwaves, indicated by thick solid arrows M12a, are generated at the 5 th coupling point P5, and microwaves, indicated by thin solid arrows M12b, are generated at the 4 th coupling point P4. The reason why the solid arrow M12b is made thinner is the same as the reason why the solid arrow M3 is made thinner.

When the effective propagation time of the microwave based on the microstrip line 13 between the 3 rd coupling point P3 and the 5 th coupling point P5 is designed as time t1, the microwave generated at the 3 rd coupling point P3 at the time shown in (a) of fig. 11 propagates to the 5 th coupling point P5 at the time shown in (b) of fig. 11. That is, at the time shown in fig. 11 (b), microwaves indicated by thick solid arrows M11 and microwaves indicated by thick solid arrows M12a are generated at the 5 th coupling point P5.

Therefore, the two microwaves are added and propagated through the microstrip line 13 toward the 2 nd output unit 132, and after a predetermined time has elapsed, the two microwaves are output to the 2 nd output unit 132. Since the effective propagation time is set to the time t1, the distance of the 1 st transmission line 13a farther from the tube axis L1 than the parallel line L4 is set to the effective length λ in the present embodiment _re1/4 of (1). The microwave generated at the 4 th coupling point P4 and indicated by a thin solid arrow M12b propagates through the microstrip line 13 toward the 1 st output unit 131, and is output to the 1 st output unit 131 after a predetermined time has elapsed.

At time T shown in fig. 11 (c), T0+ T/2+ T1/2, the cross opening 11 is excited by a magnetic field indicated by a broken-line arrow B34, and a microwave indicated by a thin solid-line arrow M13B is generated at the 3 rd coupling point P3. The microwave propagates through the microstrip line 13 toward the 1 st output section 131. The reason why the thickness of the solid arrow M13b is reduced is the same as the reason why the thickness of the solid arrow M3 is reduced.

At time T shown in fig. 11 (d), T0+ T/2+ T1+ T1/2, cross hatch 11 is excited by a magnetic field indicated by a broken-line arrow B41. Microwaves, indicated by the thin solid arrow M14b, are generated at the 5 th coupling point P5, and microwaves, indicated by the thick solid arrow M14a, are generated at the 4 th coupling point P4. The microwave represented by the thin solid arrow M14b propagates in the microstrip line 13 toward the 3 rd coupling point P3. The reason why the thickness of the solid arrow M14b is reduced is the same as the reason why the thickness of the solid arrow M3 is reduced.

The microwave represented by the thick solid arrow M14a propagates in the microstrip line 13 toward the 3 rd coupling point P3. When the effective propagation time of the microwave based on the microstrip line 13 between the 3 rd coupling point P3 and the 4 th coupling point P4 is designed as time t1, the microwave generated at the 3 rd coupling point P3 at the time shown in (c) of fig. 11 propagates to the 4 th coupling point P4 at the time shown in (d) of fig. 11.

That is, at the time shown in fig. 11 (d), microwaves indicated by a thin solid arrow M13b and microwaves indicated by a thick solid arrow M14a are generated at the 4 th coupling point P4. In order to set the effective propagation time to the time t1, in the present embodiment, the distance of the 2 nd transmission line 13b farther from the tube axis L1 than the parallel line L4 is set to the effective length λ _re1/4 of (1).

That is, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b farther from the tube axis L1 than the parallel line L4 is set to the effective length λ _re1/2 of (1). The microwave represented by the thinner solid arrow M13b propagates in the opposite direction to the microwave represented by the thicker solid arrow M14 a. Therefore, the microwaves indicated by the thin solid arrow M13b are cancelled and reduced, and are not output to the 1 st output unit 131.

At time T, T0+ T1/2, intersection 11 is excited by a magnetic field indicated by a broken-line arrow B12, in the same manner as at time T, T0+ T1/2 shown in fig. 11 (a). In this case, the microwave represented by a thin solid arrow M14b, which is not described in the case of the time shown in fig. 11 (a), exists on the microstrip line 13.

The microwave, which is indicated by a thin solid arrow M14b, propagates to the 3 rd coupling point P3 at time T0+ T1/2. The microwave represented by the thinner solid arrow M14b propagates in the opposite direction to the microwave represented by the thicker solid arrow M11 and the thicker solid arrow M14 a. Therefore, the microwaves indicated by the thin solid arrow M14b are cancelled and reduced, and are not output to the 1 st output unit 131.

Strictly speaking, the amount of microwaves propagating from the 3 rd coupling point P3 at time t (t 0+ t 1/2) is obtained by subtracting the amount of microwaves indicated by the thin solid arrow M14b from the amount of microwaves indicated by the thick solid arrows M11 and M14a (M11+ M14a-M14 b). Therefore, the amount of microwaves output to the 2 nd output unit 132 is obtained by adding the amount of microwaves propagating from the 3 rd coupling point P3 to the amount of microwaves indicated by the thick solid arrow M12a (M11+ M12a + M14a-M14 b).

Even if this is considered, the amount of microwaves (M11+ M12a + M14a-M14b) output to the 2 nd output part 132 is much more than the amount of microwaves (M12b) output to the 1 st output part 131. Therefore, the microstrip line 13 outputs most of the microwaves radiated counterclockwise from the cross opening 11 by the reflected waves propagating in the direction of the arrow 31 to the 2 nd output unit 132. On the other hand, the microstrip line 13 outputs most of the microwaves radiated in the clockwise direction from the intersection 11 by the incident wave propagating in the direction of the arrow 30 to the 1 st output unit 131.

In the present embodiment, the incident wave detection unit and the reflected wave detection unit share the microstrip line 13, the microstrip line 13 faces the intersection opening 11, and the intersection opening 11 is disposed on the wall surface of the waveguide 10. The incident wave detection unit extracts an incident wave from one end of the microstrip line 13. The reflected wave detector extracts the reflected wave from the other end of the microstrip line 13. With this configuration, the incident wave detection unit and the reflected wave detection unit can be downsized.

In the present embodiment, the directional coupler 6 has the intersection opening 11, and the intersection opening 11 is disposed at a position not intersecting the tube axis L1 of the waveguide 10 in a plan view, and radiates circularly polarized microwaves. According to this structure, the rotation directions of the circularly polarized microwaves radiated from the cross aperture 11 are opposite to each other in the incident wave and the reflected wave. The incident wave and the reflected wave can be separated and detected by utilizing the difference in the rotation direction of the circularly polarized microwave.

In the directional coupler 6 of the present embodiment, the 1 st transmission line 13a has the 1 st straight line part 13aa, and the 2 nd transmission line 13b has the 2 nd straight line part 13 ba. With this configuration, the bent portion of the microstrip line 13 can be reduced more than before. The necessity of bending the microstrip line 13 at a right angle can be eliminated. The portion where the microstrip line 13 is bent can be separated from the region in the vertical direction of the intersection opening 11. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the 1 st transmission line 13a and the 2 nd transmission line 13b are connected to each other at the following positions: this position is outside the rectangular area E1 in top view and is away from the tube axis L1. With this configuration, the portion where the microstrip line 13 is bent can be further separated from the region in the vertical direction of the intersection opening 11. The 1 st and 2 nd linear portions 13aa and 13ba can be further extended, and the flow of current flowing through the microstrip line 13 can be suppressed from being obstructed. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the 1 st linear portion 13aa intersects the 1 st long hole 11e at a position closer to the aperture distal end portion 11ea than the aperture center portion 11c in a plan view. The 2 nd straight portion 13ba intersects the 2 nd long hole 11f at a position closer to the opening distal end portion 11fa than the opening center portion 11c in a plan view. Normally, a stronger magnetic field is generated around the opening end portions 11ea and 11fa than around the opening center portion 11 c. According to the above structure, a stronger magnetic field is coupled to the microstrip line 13. Therefore, the current flowing through the microstrip line 13 increases more. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the 1 st linear portion 13aa is perpendicular to the 1 st long hole 11e in a plan view. According to this configuration, the propagation direction of the microwave indicated by the solid arrow M1 generated at the 1 st coupling point P1 is made to be the same as the rotation direction 32 of the microwave radiated from the cross hatch 11. This can increase the amount of microwaves indicated by the solid arrow M1.

The propagation direction of the microwave generated at the 1 st coupling point P1 and indicated by the solid arrow M3 is made opposite to the rotation direction 32 of the microwave radiated from the cross hatch 11. This can reduce the amount of microwaves indicated by the solid arrow M3. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the 2 nd linear portion 13ba is perpendicular to the 2 nd long hole 11f in a plan view. According to this configuration, the propagation direction of the microwave indicated by the solid arrow M2 generated at the 2 nd coupling point P2 is made to be the same as the rotation direction 32 of the microwave radiated from the cross hatch 11. This can further increase the amount of microwaves indicated by the solid arrow M2.

The propagation direction of the microwave generated at the 2 nd coupling point P2 and indicated by the solid arrow M4 is made opposite to the rotation direction 32 of the microwave radiated from the cross hatch 11. This can further reduce the amount of microwaves indicated by the solid arrow M4. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the microstrip line 13 includes a1 st straight line portion 13aa, a 2 nd straight line portion 13ba, a 3 rd straight line portion 13ab, and a 4 th straight line portion 13 bb. The 1 st and 3 rd linear portions 13aa and 13ab adjacent to each other are connected to form an obtuse angle. The 2 nd and 4 th linear portions 13ba and 13bb adjacent to each other are connected to form an obtuse angle.

With this configuration, the portions bent at right angles in the microstrip line 13 can be reduced. This can suppress the flow of current in the coupling line from being blocked. As a result, the incident wave and the reflected wave can be separated and detected with higher accuracy.

In the directional coupler 6 of the present embodiment, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b that are farther from the tube axis L1 than the virtual straight line L3 is set to the effective length λ _re1/4 of (1). With this configuration, the incident wave and the reflected wave can be separated and detected with higher accuracy. Setting the total distance as an effective length lambda_reThe effective length λ may be set to approximately 1/4, but need not necessarily be set to the effective length λ _re1/4 of (1).

In the directional coupler 6 of the present embodiment, the total distance of the 1 st transmission line 13a and the 2 nd transmission line 13b that are farther from the tube axis L1 than the parallel line L4 is set to the effective length λ _re1/2 of (1). With this configuration, the incident wave and the reflected wave can be separated and detected with higher accuracy. Setting the total distance as an effective length lambda_reAbout 1/2 may be, but need not necessarily be, set to the effective length λ _re1/2 of (1).

As shown in fig. 8, in the present embodiment, one end of the 1 st transmission line 13a and one end of the 2 nd transmission line 13b are connected so as to form a right angle. However, the present disclosure is not limited thereto. One end of the 1 st transmission line 13a may be connected to one end of the 2 nd transmission line 13b at a position other than the region of the intersection opening 11 in plan view. In this region, the influence due to the magnetic field is large.

Fig. 12 to 17 are plan views showing modifications 1 to 6 of the microstrip line 13. As shown in fig. 12, the 1 st transmission line 13a and the 2 nd transmission line 13b may be bent such that a connection point between one end of the 1 st transmission line 13a and one end of the 2 nd transmission line 13b is distant from the opening center portion 11 c.

As shown in fig. 13, the 1 st transmission line 13a and the 2 nd transmission line 13b may be bent such that a connection point between one end of the 1 st transmission line 13a and one end of the 2 nd transmission line 13b is close to the open center portion 11 c. As shown in fig. 14, the 1 st transmission line 13a and the 2 nd transmission line 13b may be bent such that a connection point between one end of the 1 st transmission line 13a and one end of the 2 nd transmission line 13b is close to the open center portion 11 c.

In the present embodiment, the 1 st linear portion 13aa and the 2 nd linear portion 13ba correspond to the 1 st intersecting line portion and the 2 nd intersecting line portion, respectively. However, the present disclosure is not limited thereto. As shown in fig. 15, the 1 st and 2 nd intersecting line portions may be arc-shaped portions 13ac and 13bc, respectively.

In the present embodiment, the 3 rd and 4 th linear portions 13ab and 13bb are parallel to the perpendicular line L2. However, the present disclosure is not limited thereto. As shown in fig. 16, the 3 rd and 4 th linear portions 13ab and 13bb may be parallel to the parallel line L4.

In the present embodiment, the 1 st transmission line 13a and the 2 nd transmission line 13b have a plurality of straight portions. However, the present disclosure is not limited thereto. As shown in fig. 17, the 1 st transmission line 13a and the 2 nd transmission line 13b may be formed of a single straight line portion.

In the present embodiment, the intersection opening 11 is formed line-symmetrically with respect to the perpendicular line L2. The perpendicular line L2 is perpendicular to the tube axis L1 and passes through the opening center portion 11 c. However, the present disclosure is not limited thereto. The intersection opening 11 may not be formed line-symmetrically with respect to the perpendicular line L2. For example, the 1 st long hole 11e and the 2 nd long hole 11f may intersect at positions deviated from the respective longitudinal center portions. The length of the 1 st long hole 11e and the length of the 2 nd long hole 11f may be different from each other.

In these cases, the opening intersection portion where the 1 st long hole 11e and the 2 nd long hole 11f intersect is offset from the opening center portion 11 c. The intersection opening 11 may be formed to be symmetrical with respect to a straight line slightly inclined with respect to the perpendicular line L2 in a plan view.

(New findings concerning the arrangement of the standing wave and reflected wave detecting section in the pipe)

Fig. 19 is a plan view of the orthogonal waveguide 251 for checking the reflected wave detection accuracy based on the position of the reflected wave detection unit. As shown in fig. 19, the orthogonal waveguide 251 has a main waveguide 252 and a sub-waveguide 253. The secondary waveguide 253 is perpendicular to the primary waveguide 252 and is coupled to the primary waveguide 252 via an X-shaped opening 254 and an opening 255.

In order to quantitatively measure the reflected wave using the network analyzer, the end 256 of the main waveguide 252 is closed and short-circuited. The microwave 257 incident from port Q (not shown) of the network analyzer is totally reflected by the end 256.

A portion of the reflected wave returns to port Q. The remaining reflected waves are transmitted to the sub-waveguide 253 through the openings 254 and 255, and are divided into microwaves 258 and 259 in the sub-waveguide 253. The microwaves 258 are transmitted to a port S (not shown) of the network analyzer, and the microwaves 259 are transmitted to a port T (not shown) of the network analyzer.

The primary waveguide 252 and the secondary waveguide 253 each have a symmetrical shape. The openings 254, 255 have the same shape. The openings 254 and 255 are arranged symmetrically with respect to both the main waveguide 252 and the sub-waveguide 253. Therefore, the amount of microwaves 258 is equal to the amount of microwaves 259.

The primary 252 and secondary 253 waveguides have a waveguide width (commonly referred to as the a-dimension) of about 100 mm. The in-tube wavelength λ g of the microwaves in the primary waveguide 252 and the secondary waveguide 253 is about 154 mm.

The actually observed S parameter is a general observed value of the network analyzer. Specifically, a ratio S31 of the microwave 258 transmitted to the port S with respect to the microwave 257 incident from the port Q, and a ratio S41 of the microwave 259 transmitted to the port T with respect to the microwave 257 incident from the port Q were observed by the network analyzer. Ratios S31, S41 are often described in decibels because they are much less than 1.

The ratios S31, S41 were measured using microwaves of frequencies of 2450 to 2500MHz while changing the distance Lsf from the tip 256 to the openings 254, 255 of the main waveguide 252. Fig. 20 plots the results. The horizontal axis represents the distance Lsf [ mm ], and the vertical axis represents the ratios S31, S41[ dB ]. The results were examined.

In the main waveguide 252, a node of the in-tube standing wave is generated at the closed end 256, and a node is generated from the end 256 at 1/2(═ 77mm) of the in-tube wavelength λ g. Therefore, when the distance Lsf is 154mm, the openings 254 and 255 are arranged at the node positions.

Since an antinode is generated at a position deviated from the node by λ g/4(═ 38.5mm), the openings 254 and 255 are arranged at the position of the antinode when the distance Lsf is 115.5mm (═ λ g × 3/4) and 192.5mm (═ λ g × 5/4). The present inventors have found two features as described below based on the characteristic diagram.

The first feature relates to sensitivity. When the aperture is located at the node position (distance Lsf 154mm), the ratios S31, S41 are-12 to-21 dB. When the aperture is located at the anti-node position (the distance Lsf is 115.5mm or 192.5mm), the ratios S31 and S41 are-4 to-8 dB. Therefore, the ratios S31, S41 in the case where the openings are arranged at the antinode positions are larger than the ratios S31, S41 in the case where the openings are arranged at the node positions.

That is, the present inventors have found that when the aperture is disposed at the antinode, the reflected wave detected from the aperture increases, and the sensitivity improves. When compared with the average of the six graphs shown in fig. 20, the difference between the ratio of the case where the opening is located at the node (about-16 dB) and the ratio of the case where the opening is located at the antinode (about-6 dB) is 10 dB. That is, when the aperture is disposed at the anti-node position, the sensitivity is 10 times higher than when the aperture is disposed at the node position.

The second feature relates to stability with respect to frequency. When the aperture is located at the node position (distance Lsf: 154mm), the ratios S31, S41 observed in accordance with the frequency change are-12 to-21 dB. When the aperture is located at the anti-node position (the distance Lsf is 115.5mm or 192.5mm), the ratios S31 and S41 observed according to the frequency change are-4 to-8 dB.

Therefore, the fluctuation widths (about 4dB) of the ratios S31, S41 in the case where the openings are located at the antinode positions are smaller than the fluctuation widths (about 9dB) of the ratios S31, S41 in the case where the openings are located at the node positions. That is, the present inventors have found that when the aperture is disposed at the antinode, the stability of the reflected wave detected from the aperture with respect to the frequency is improved.

As described above, by detecting the reflected wave at the antinode of the standing wave in the pipe, the sensitivity and the stability with respect to the frequency can be improved. As a result, the state of the object 1 can be detected more accurately.

Next, a case where an opening is arranged at a position between an antinode position (distance Lsf is 115.5mm, 192.5mm) and a node position (distance Lsf is 154mm) is considered.

As shown in fig. 20, the ratios S31 and S41 in the case where the aperture is arranged at the intermediate position between the antinode and the node (distance Lsf is 134.75mm or 173.25mm) are not as poor as in the case where the aperture is arranged at the node position (distance Lsf is 154 mm). The ratios S31 and S41 in this case are generally quite good as close to the case where the openings are arranged at the antinode positions (the distance Lsf is 115.5mm and 192.5 mm).

That is, the measurement result is very poor only when the opening is arranged near the node position (distance Lsf is 154 mm). Therefore, as long as no opening is provided at the node position, the detection accuracy of the reflected wave can be improved to some extent.

More safely, when the aperture is disposed closer to the antinode position than the intermediate position between the antinode and the node (distance Lsf 134.75mm, 173.25mm), the detection accuracy of the reflected wave can be improved. These positions are spaced forward and backward from the exact antinode position of the standing wave in the pipe (or the central position of the two nodes) by 1/8 or less of the wavelength λ g in the pipe.

Specifically, the ratios S31, S41 at these locations are approximately in the range of-5 to-9 dB. Regarding the sensitivity, the average value of the six graphs shown in fig. 20 is about-16 dB in the case where the opening is arranged at the node position, about-6 dB in the case where the opening is arranged at the antinode position, and about-7 dB in the case where the opening is arranged at the intermediate position between the antinode and the node.

That is, the ratios S31 and S41 in the case where the aperture is disposed at the intermediate position between the antinode and the node are 9dB better than in the case where the aperture is disposed at the node position, and the difference from the case where the aperture is disposed at the antinode position is no more than 1 dB.

Regarding the stability with respect to frequency, the fluctuation width of the six graphs shown in fig. 20 is about 9dB in the case where the opening is arranged at the node position, about 2dB in the case where the opening is arranged at the antinode position, and about 4dB in the case where the opening is arranged at the intermediate position between the antinode and the node.

That is, the ratios S31 and S41 in the case where the openings are arranged at the intermediate positions between the antinode and the node are far superior to the case where the openings are arranged at the node position, and are generally close to the case where the openings are arranged at the antinode position. Therefore, by arranging the opening at a position spaced forward and backward from the anti-node position (or the central position of the two nodes) by 1/8 or less of the in-tube wavelength λ g, the detection accuracy of the reflected wave can be improved.

(modes and effects of the present disclosure)

With reference to fig. 21, the positional relationship between the arrangement of the standing wave in the tube and the reflected wave detection unit and the respective aspects of the present disclosure will be described. Fig. 21 is an enlarged view of the periphery of the waveguide 10 in fig. 1.

As shown in fig. 21, a microwave heating device according to one embodiment of the present disclosure includes a heating chamber 2 for accommodating an object to be heated, a magnetron 3 for generating microwaves, a waveguide 10, and a directional coupler 6.

The waveguide 10 transmits the microwave generated by the magnetron 3 to the heating chamber. The directional coupler 6 is disposed in the vicinity of an antinode 302 of an intra-pipe standing wave 301 generated in the waveguide 10. The directional coupler 6 includes a reflected wave detector that detects a part of the reflected wave, which is the microwave returned from the heating chamber 2 to the magnetron 3.

Antinodes 302 and nodes 303 of the standing wave 301 in the pipe alternately appear at 1/4 for each wavelength λ g in the pipe.

According to this configuration, the reflected wave can be detected in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to one embodiment of the present disclosure, the center portion of the rectangular region E1 circumscribed with the intersection opening 11 is disposed between the two nodes 303 of the in-pipe standing wave 301, and the directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-pipe standing wave 301.

According to this configuration, the reflected wave can be detected in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

It is difficult to determine the position of the anti-node 302 of the invisible standing wave 301 in the pipe. The positioning of the directional coupler 6 can be easily performed if the position between the adjacent two nodes 303 is taken as a reference.

In the microwave heating device according to one embodiment of the present disclosure, the rectangular region E1 circumscribed with the intersection opening 11 is arranged so as not to overlap with the two nodes 303 of the in-pipe standing wave 301, and the directional coupler 6 including the reflected wave detection unit is arranged in the vicinity of the antinode 302 of the in-pipe standing wave 301.

According to this structure, the reflected wave can be detected at a position closer to the antinode 302 of the intra-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to one embodiment of the present disclosure, the directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-pipe standing wave 301 by being spaced apart from the center position of the two nodes 303 of the in-pipe standing wave 301 by 1/8 or less of the in-pipe wavelength λ g in the front-rear direction.

As described with reference to fig. 20, if the position is spaced forward and backward from the anti-node 302 by 1/8 or less of the tube internal wavelength λ g, the reflected wave can be detected with a certain degree of accuracy. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to one embodiment of the present disclosure, the directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-tube standing wave 301 by being spaced apart from the end 304 of the waveguide 10 by a distance equal to an odd multiple (3 times in fig. 21) of the in-tube wavelength λ g that is 1/4.

According to this configuration, the reflected wave can be detected in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

The microwave heating device according to one embodiment of the present disclosure further includes a standing wave stabilizer 5, and the standing wave stabilizer 5 stabilizes the position of the in-tube standing wave 301 generated in the waveguide 10. The directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-pipe standing wave 301 by being spaced apart from the standing wave stabilizer 5 by a distance of an odd multiple (1 time in fig. 21) of 1/4 of the in-pipe wavelength λ g.

According to this configuration, the reflected wave can be detected in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to one embodiment of the present disclosure, the standing wave stabilizer 5 is constituted by a protrusion protruding into the waveguide 10.

In the present structure, a node 303 of the intra-pipe standing wave 301 is generated at the position of the protrusion. The directional coupler 6 including the reflected wave detection section is disposed at a distance of an odd multiple of 1/4 of the in-pipe wavelength λ g from the protrusion section, thereby detecting the reflected wave in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to the embodiment of the present disclosure, the waveguide 10 may have a bent portion 10b (see fig. 3) bent in an L-shape, and the standing wave stabilizing portion may be formed of the bent portion 10 b.

In the present structure, a node 303 of the intra-pipe standing wave 301 is generated at the position of the bent portion 10 b. The directional coupler 6 including the reflected wave detection section is disposed at a distance of an odd multiple of 1/4 of the in-tube wavelength λ g from the bent section 10b, and detects the reflected wave at the position of the antinode 302 of the in-tube standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating apparatus according to one embodiment of the present disclosure, the directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-pipe standing wave 301 by being spaced apart from the coupling position 305 of the magnetron 3 and the waveguide 10 by a distance equal to an integral multiple (2 times in fig. 21) of 1/2 of the in-pipe wavelength λ g.

In the present structure, an antinode 302 of the standing wave 301 in the pipe is generated at the coupling position 305. The directional coupler 6 including the reflected wave detection unit is disposed at a distance of an integral multiple of 1/2 of the in-pipe wavelength λ g from the coupling position 305, and detects the reflected wave in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

A microwave heating device according to one embodiment of the present disclosure includes an antenna 4, and the antenna 4 radiates microwaves transmitted through a waveguide 10 to a heating chamber 2. The directional coupler 6 including the reflected wave detection unit is disposed in the vicinity of the antinode 302 of the in-pipe standing wave 301 by being spaced apart from the coupling position 306 of the antenna 4 and the waveguide 10 by a distance equal to an integral multiple (1 time in fig. 21) of 1/2 of the in-pipe wavelength λ g.

In the present structure, an antinode 302 of a standing wave 301 in the pipe is generated at a coupling position 306. The directional coupler 6 including the reflected wave detection unit is disposed at a distance equal to an integral multiple of 1/2 of the in-pipe wavelength λ g from the coupling position 306, and detects the reflected wave in the vicinity of the antinode 302 of the in-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In a microwave heating device according to an aspect of the present disclosure, a directional coupler 6 including a reflected wave detection unit includes: a cross opening 11 provided in the waveguide 10; and a coupling line opposite to the cross opening 11 (see fig. 8). The crossover opening 11 is disposed in the vicinity of an antinode 302 of the standing wave 301 in the pipe.

According to this configuration, the reflected wave can be detected at the position of the antinode 302 of the intra-pipe standing wave 301. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

In the microwave heating device according to one embodiment of the present disclosure, the intersecting opening 11 includes the 1 st long hole 11e and the 2 nd long hole 11f (see fig. 7 and 8) that intersect with each other, and is provided at a position that does not intersect with the tube axis of the waveguide 10 in a plan view. An opening intersection portion (see fig. 7 and 8) where the 1 st long hole 11e and the 2 nd long hole 11f intersect is arranged in the vicinity of an antinode 302 of the in-pipe standing wave 301.

According to this configuration, the microwave transmitted through the waveguide 10 is radiated to the heating chamber 2 as a circularly polarized microwave whose electric field direction rotates around the opening intersection. Since the circularly polarized microwaves have opposite rotation directions in the incident wave and the reflected wave, the incident wave and the reflected wave can be easily separated. In addition, in the present configuration, the reflected wave is detected in the vicinity of the antinode 302 of the intraductal standing wave. This improves the detection accuracy of the reflected wave, and can detect the state of the object 1 more accurately.

Industrial applicability

The present disclosure can be applied to a microwave heating apparatus for home use or commercial use.

Description of the reference symbols

1: an object to be heated; 2: a heating chamber; 2 a: a mounting table; 3: a magnetron; 4: an antenna; 5: a standing wave stabilizing section; 6. 60: a directional coupler; 7: a control unit; 7 a: a signal; 8: a drive power supply; 9: a motor; 10: a waveguide; 10 a: a wide breadth; 10 b: a bending section; 10 d: a magnetic field distribution; 11: a cross opening; 11 c: an open central portion; 11 d: a width; 11 e: a1 st long hole; 11ea, 11 fa: an opening end portion; 11 f: a 2 nd long hole; 11 w: a length; 12: a printed substrate; 12 a: a front surface of the substrate; 12 b: the reverse side of the substrate; 13: a microstrip line; 13 a: 1 st transmission line; 13 aa: a1 st straight line part; 13 ab: a 3 rd linear part; 13ac, 13 bc: a circular arc portion; 13 b: a 2 nd transmission line; 13 ba: a 2 nd straight line part; 13 bb: a 4 th linear part; 14: a support portion; 15: a1 st detector circuit; 16: a 2 nd detection circuit; 18: a1 st detection output unit; 18a, 19 a: a connector; 19: a 2 nd detection output section; 50: a microwave heating device; 131: a1 st output unit; 132: a 2 nd output unit; 141. 142: a groove; 251: an orthogonal waveguide; 252: a main waveguide; 253: a secondary waveguide; 254. 255: an opening; 256. 304: a terminal end; 257. 258, 259: microwave; 301: standing waves in the pipe; 302: an anti-node; 303: a node; 305. 306: a coupling position; e1: a rectangular area; l1: a tubular shaft; l2: a vertical line; l3: an imaginary straight line; l4: parallel lines; p1: 1 st coupling point; p2: a 2 nd coupling point; p3: a 3 rd coupling point; p4: a 4 th coupling point; p5: the 5 th coupling point.

The claims (modification according to treaty clause 19)

(modified) a microwave heating apparatus having:

a heating chamber configured to accommodate an object to be heated;

a microwave generating unit configured to generate microwaves;

a waveguide configured to transmit the microwaves generated by the microwave generating unit to the heating chamber;

a reflected wave detection unit arranged in the vicinity of an antinode of a standing wave generated in the waveguide and configured to detect a part of a reflected wave, the reflected wave being the microwave returned from the heating chamber to the microwave generation unit; and

a standing wave stabilizer configured to stabilize a position of a standing wave in the pipe,

the reflected wave detection unit is disposed at a distance from the standing wave stabilization unit that is an odd multiple of 1/4 of the in-tube wavelength of the in-tube standing wave.

2. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed between two nodes of the standing wave in the pipe, and is thereby disposed in the vicinity of the antinode of the standing wave in the pipe.

3. The microwave heating apparatus according to claim 2,

the reflected wave detection unit is disposed so as not to overlap the two nodes of the intra-pipe standing wave, and is thereby disposed in the vicinity of the antinode of the intra-pipe standing wave.

4. The microwave heating apparatus according to claim 3,

the reflected wave detection unit is disposed in the vicinity of the antinode of the standing wave in the pipe by being spaced from the center position of the two nodes of the standing wave in the pipe by 1/8 or less of the wavelength in the pipe of the standing wave in the pipe.

5. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the end of the waveguide by a distance that is an odd multiple of 1/4 times the intra-tube wavelength of the intra-tube standing wave.

(deletion)

(modified) the microwave heating apparatus according to claim 1, wherein,

the standing wave stabilizer is constituted by a protrusion protruding into the waveguide.

(modified) the microwave heating apparatus according to claim 1, wherein,

the waveguide tube has a bent portion bent in an L shape, and the standing wave stabilizing portion is constituted by the bent portion.

9. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the coupling position of the microwave generation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the intra-tube wavelength of the intra-tube standing wave.

10. The microwave heating apparatus according to claim 1,

the microwave heating apparatus further includes a microwave radiation unit configured to radiate the microwaves transmitted through the waveguide to the heating chamber,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the coupling position of the microwave radiation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the intra-tube wavelength of the intra-tube standing wave.

11. The microwave heating apparatus according to claim 1,

the reflected wave detection unit includes: an opening portion provided in the waveguide; and a coupling line facing the opening,

the opening is disposed in the vicinity of the antinode of the standing wave in the pipe.

12. The microwave heating apparatus according to claim 11,

the opening includes a1 st long hole and a 2 nd long hole intersecting with each other and is provided at a position not intersecting with a tube axis of the waveguide in a plan view, and an opening intersection portion where the 1 st long hole and the 2 nd long hole intersect is disposed in the vicinity of the antinode of the in-tube standing wave.

Claims (12)

1. A microwave heating device, comprising:

a heating chamber configured to accommodate an object to be heated;

a microwave generating unit configured to generate microwaves;

a waveguide configured to transmit the microwaves generated by the microwave generating unit to the heating chamber; and

and a reflected wave detection unit arranged in the vicinity of an antinode of a standing wave generated in the waveguide and configured to detect a part of a reflected wave, the reflected wave being the microwave returned from the heating chamber to the microwave generation unit.

2. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed between two nodes of the standing wave in the pipe, and is thereby disposed in the vicinity of the antinode of the standing wave in the pipe.

3. The microwave heating apparatus according to claim 2,

the reflected wave detection unit is disposed so as not to overlap the two nodes of the intra-pipe standing wave, and is thereby disposed in the vicinity of the antinode of the intra-pipe standing wave.

4. The microwave heating apparatus according to claim 3,

the reflected wave detection unit is disposed in the vicinity of the antinode of the standing wave in the pipe by being spaced from the center position of the two nodes of the standing wave in the pipe by 1/8 or less of the wavelength in the pipe of the standing wave in the pipe.

5. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the end of the waveguide by a distance that is an odd multiple of 1/4 times the intra-tube wavelength of the intra-tube standing wave.

6. The microwave heating apparatus according to claim 1,

the microwave heating device further includes a standing wave stabilizer configured to stabilize a position of the in-tube standing wave, and the reflected wave detector is disposed in the vicinity of the antinode of the in-tube standing wave by being spaced apart from the standing wave stabilizer by a distance that is an odd multiple of 1/4 of an in-tube wavelength of the in-tube standing wave.

7. The microwave heating apparatus according to claim 6,

the standing wave stabilizer is constituted by a protrusion protruding into the waveguide.

8. The microwave heating apparatus according to claim 6,

the waveguide tube has a bent portion bent in an L shape, and the standing wave stabilizing portion is constituted by the bent portion.

9. The microwave heating apparatus according to claim 1,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the coupling position of the microwave generation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the intra-tube wavelength of the intra-tube standing wave.

10. The microwave heating apparatus according to claim 1,

the microwave heating apparatus further includes a microwave radiation unit configured to radiate the microwaves transmitted through the waveguide to the heating chamber,

the reflected wave detection unit is disposed in the vicinity of the antinode of the intra-tube standing wave by being spaced apart from the coupling position of the microwave radiation unit and the waveguide by a distance equal to an integral multiple of 1/2 of the intra-tube wavelength of the intra-tube standing wave.

11. The microwave heating apparatus according to claim 1,

the reflected wave detection unit includes: an opening portion provided in the waveguide; and a coupling line facing the opening,

the opening is disposed in the vicinity of the antinode of the standing wave in the pipe.

12. The microwave heating apparatus according to claim 11,

the opening includes a1 st long hole and a 2 nd long hole intersecting with each other and is provided at a position not intersecting with a tube axis of the waveguide in a plan view, and an opening intersection portion where the 1 st long hole and the 2 nd long hole intersect is disposed in the vicinity of the antinode of the in-tube standing wave.

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